HOROLOGY being one of the oldest arts and branches of science, it is almost inevitable that advances in it should be of a mediocre and modest character, and not of a nature to claim great attention in these days of startling and sensational discovery. But nevertheless during the period we refer to much good work has been done. In chronometers, the secondary compensation error has been discovered and means found to rectify it. In clocks, the same has been done for the barometric error. Moreover, the difficulties connected with the correct working of gravity escapements have been overcome; so that scarcely a good turret clock is made without one now. Electricity also has been largely applied for driving or controlling clocks, or for controlling chronometers; and the measurement of minute fractions of a second has been attained by chronographic appliances of extreme accuracy. Articles explanatory of these subjects have appeared in the pages of NATURE 1 from time to time. In addition there has been a mass of subsidiary improvements which it is impossible to classify, and of which we shall have to describe the leading features in a somewhat desultory manner in the succeeding pages.